3.1.2 Transport in animals - circulatory systems Flashcards
Why are specialised systems for multicellular organisms needed?
- The metabolic demands of most multicellular organisms are high, therefore diffusion over long distances is not enough to supply the quantities needed.
- The surface area to volume (SA:V) ratio gets smaller as multicellular organisms get bigger, so the diffusion distances get bigger whilst the surface area for absorption becomes smaller.
- Molecules such as hormones or enzymes may be made in one place but needed in another.
- Food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism.
- Waste products of metabolism need to be removed from the cells and transported to excretory organs
Define Mass transport system
When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body.
Define Haemocoel
open cavity
DEfine Haemolymph
insect blood
What circulatory system do large multicellular organisms have?
Most large multicellular organisms have specialised circulatory systems, which carry oxygen, carbon dioxide, nutrients, waste products and hormones around the body.
Explain how an open circulatory system works.
In an open circulatory, the transport medium (e.g. blood) is pumped straight from the heart into the body cavity of the animal.
Haemolymph, flows freely through the body cavity and makes direct contact with organs and tissues. The insect circulation system does not carry oxygen, so the blood does not contain red blood cells as ours does, therefore haemolymph is usually green or yellow. A single blood vessel runs along the dorsal side of the insect. Few little umps (hearts) push the haemolymph through this vessel (in one direction) to the haemocoel. The haemolymph is then re-absorbed by the dorsal vessel.
What organism has an open circulatory system?
Insects
Describe how a closed circulatory system works.
In a closed circulatory system, the blood is enclosed in blood vessels and does not come directly into contact with the cells of the body. The heart pumps the blood around the body under pressure and relatively quickly, and the blood returns directly to the heart. Substances leave and enter the blood by diffusion through the walls of the blood vessels.
How can the amount of blood flowing to a particular tissue be adjusted?
By widening or narrowing blood vessels.
What organism has a closed circulatory system?
Earthworms
What are the major blood vessels in a closed circulatory system?
The major blood vessels are:
- Ventral blood vessel – distributes the blood to various parts of the body.
- Branches of the ventral blood vessel – take the blood to all the structures within each segment.
- Dorsal blood vessel – collects the blood from the body
The blood contains and oxygen-carrying pigment.
There is a heart and 5 pseudo-hearts to pump the blood around.
Explain a single circulatory system.
In single circulatory systems the blood flows through the heart and is pumped out to travel all around the body before returning to the heart.
Blood passes through heart once per complete circuit.
Why is a single circulatory system effective for fish?
Efficient for the level of activity of fish but not mammals. Also fish do not maintain their body temperature and they need to respire relatively less compared to mammals.
Explain a double circulatory system.
Heart is composed of two separate pumps – right side pumps blood to the lungs to pick up oxygen; blood is returned to the left side; left side pumps oxygenated blood rapidly and at high pressure to the body; the blood is returned to the right side.
In a double circulatory system, the blood travels twice through the heart for each circuit of the body (each circuit to the lungs and to the body), but only passes one capillary network which means a relatively high pressure and fast flow of blood can be maintained.
Why is a double circulatory system necessary for mammals?
This is necessary because of the higher level of activity (energy) and need to maintain their body temperature at 370 through respiration. Mammals need to deliver and remove materials to and from cells rapidly – achieved by delivering blood at high pressure to tissues.
